The present invention relates generally to the adhering of a component, such as an electronic, electric or optical component to a surface using an adhesive or a cement. More specifically, the present invention relates to a method for bonding a component to a surface using an epoxy-based cement or adhesive made in accordance with the present invention.
In many technical fields, workpieces are already being connected and fastened exclusively by cementing. Conventional fastening methods such as soldering, welding, screwing or the like are thus being supplanted by cement or adhesives. For the constantly expanding fields of use, cements are needed which must satisfy a wide variety of requirements. In electronics and optical communications technology, reactive resins are being increasingly used for reliable and cost-effective assembly of different materials reasons of production technology, one-component systems are desirable, it being possible to employ these for bonding directly, without additional preprocessing. However, it is disadvantageous here that the one-component systems can only be rapidly hardened at increased temperatures. Short cycle times which as are necessary for an automatic production are thus difficult to achieve.
For different cementing problems, particularly in optical communications technology, a precise aligning of the components to be cemented is required. This must occur prior to the final hardening, whereby it is often necessary to fix the aligned components until hardening since the cement passes through a low-viscosity state during hardening. In addition, the cement can comprise a shrinking behavior, which in turn results in a misalignment.
Besides the de-aligning, the thermal load exhibited during the hardening of one-component reactive resins can lead to strong tensions or even to damage to the parts, or respectively, components to be cemented. In addition, the temperature sensitivity of parts that are to be cemented can limit the hardening temperature, thus necessitating cements that harden at lower temperatures.
One possibility for rapid fixing is offered by UV-hardenable cements. However, in many cases these do not comprise the necessary combination of properties that leads to a lasting, and reliable bond. Thus, in many cases a second bonding agent is employed, usually an epoxy resin, in order to guarantee the reliability and permanence of the cemented connection. This has the disadvantage that light-hardening resin and epoxy resin can be disadvantageously influenced. Furthermore, the mere need for two different bonding agents is undesirable in and of itself.
German Patent Application No. 40 38 989 teaches a bonding method with the aid of a cationically initiated hardenable epoxy resin wherein the cement is activated with the aid of UV light and can then be hardened thermally at a relatively mild temperature. It is disadvantageous in this method that a heating of the cemented location must occur for rapid fixing, and the transfer of a sufficient amount of heat is necessary. This limits the cycle times in automatic production methods. In addition, this cement hardens only where an illumination occurs, not at points where an illumination does not occur at all.
Another problem is to find a cement that is suitable for thermoplastic surfaces which enables a rapid and exact hardening.